The invention relates to an electrical lamp provided with a lamp envelope in which a light source is arranged, this lamp further comprising between the lamp envelope and an Edison lamp cap a cone-shaped lamp bowl. The bowl is composed of two halves and which is provided at its wide part with a collar enclosing the lower side of the lamp envelope, and at its narrow part with a neck-shaped portion. The outer wall of the neck portion is provided with a helically ascending rib for screwing the Edison lamp cap, after the two halves of the lamp bowl have been placed against each other. Such a lamp is known.
The known lamp is, for example, a compact low-pressure mercury vapour discharge lamp having a base at one end, as described in U.S. Pat. No. 4,383,200, in which there is arranged within the lamp envelope a fluorescent discharge tube which is sealed in a vacuum-tight manner and is curved so that the discharge path is comparatively long. Such a lamp serves as an alternative to an incandescent lamp for general illumination purposes. In this low-pressure discharge lamp are further arranged an electrical stabilization ballast and an auxiliary means for the ignition, such as a starter. These components are located, for example, within the lamp envelope or in the space limited by the lamp bowl, which preferably consists of a synthetic material.
The cone-shaped lamp bowl of the known lamp is longitudinally subdivided, and composed of two halves. This is favorable in the manufacture of the lamp because these parts readily grip around the lower side of the lamp envelope. Complicated plug-in and clamping connections between the lamp bowl and the lamp envelope are then avoided. Moreover, adhesives are superfluous. After the halves of the lamp bowl are arranged with the collar around the lower side of the envelope, an Edison lamp cap having a standardized defined pitch is screwed onto the neck of the cone-shaped lamp bowl composed of the two halves. At least by means of this Edison lamp cap, the envelope and the bowl halves are held together.
Due to the presence of a helically ascending rib with its defined pitch arranged along the whole outer circumference of the neck of the lamp bowl, the two bowl halves differ from each other. This is disadvantageous. In fact, there are not only required two differently shaped jigs for manufacturing the respective bowl halves, but special measures are also necessary during the manufacture of the lamps to prevent the two types of bowl halves from being mistaken one for the other.